The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A vehicle provided with an ISG (Idle Stop & Go) system stops an engine when the vehicle stops and starts the vehicle when the vehicle restarts in order to reduce fuel and emission.
In further detail, the vehicle provided with the ISG system automatically stops engine if idling maintains for a predetermined time after the vehicle stops, and automatically restarts the engine if a brake pedal is released or an accelerator pedal is pushed.
Since a hydraulic pump (mechanical hydraulic pump) in an automatic transmission is not operated during idle stop, hydraulic pressure is not generated in the automatic transmission of the vehicle provided with the ISG system.
If the hydraulic pressure is not generated in the automatic transmission, the hydraulic pressure cannot be supplied to friction members (clutches and brakes) operated at a first forward gear stage (gear stage at which starting control is performed) in a planetary gear set.
When a driver releases the brake pedal or pushes the accelerator pedal for restarting, the engine is automatically restarted and the hydraulic pump of the automatic transmission begins to operate to increase rotation speed.
At this time, the hydraulic pressure in the automatic transmission rises quickly and then is suddenly supplied to the friction members achieving the first gear stage. Therefore, the sudden increase of the hydraulic pressure induces impact to the friction members and the vehicle, thereby causing displeasure of the driver and damage of the friction members.
In order to inhibit or prevent such impact, a neutral state of the transmission is temporarily achieved when restarting the engine. However, we have discovered that since the hydraulic pressure is supplied to the friction members achieving the first forward gear stage after engine starting is performed at the neutral state and the hydraulic pressure is stabilized, a time delay in actually starting the vehicle is very long. Therefore, performing the temporal neutral stage while restarting the engine is rarely applied and impractical to the vehicle.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the present disclosure and therefore it may contain information that does not form the prior art that is already known to a person of ordinary skill in the art.